Sipping P. Kyzivat
Internet-Draft Cisco Systems, Inc.
Expires: October 21, 2006 April 19, 2006
Registration Event Package Extension for Session Initiation Protocol(SIP) Globablly Routeable User Agent URIs (GRUUs)draft-ietf-sipping-gruu-reg-event-04
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This draft defines an extension to RFC 3680 [2] for representing the
GRUU associated with a Contact.
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Internet-Draft Reg Event GRUU Extension April 20061. Introduction
The addition of GRUU (Globally Routable Unique URI) support to the
REGISTER message, defined in [3], introduces another element of state
to the registrar. Subscribers to the registration event package [2]
will sometimes have need for the new state.
For example, the Welcome Notices example in [2] will only operate
correctly if the contact address in the reg event notification is
reachable by the sender of the welcome notice. When the registering
device is using the GRUU extension, it is likely that the registered
contact address will not be globally addressable, and the GRUU should
be used as the target address for the MESSAGE.
Another case where this feature may be helpful is within the 3GPP IP
Multimedia Subsystem (IMS). IMS employs a technique where a REGISTER
of a contact address to one Address of Record (AOR) causes the
implicit registration of the same contact to other associated AORs.
If a GRUU is requested and obtained as part of the registration
request, then additional GRUUs will also be needed for the implicit
registrations. While assigning the additional GRUUs is
straightforward, informing the registering UA of them is not. In
IMS, UAs typically subscribe to the 'reg' event, and subscriptions to
the 'reg' event for an AOR result in notifications containing
registration state for all the associated AORs. The proposed
extension provides a way to easily deliver the GRUUs for the
associated AORs.
The reg event package has provision for including extension elements
within the <contact> element. This document defines a new element
that may be used in that context to deliver the GRUU corresponding to
the contact.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119. [1]
3. Description
A new element (<gruu>) is defined which contains a GRUU.
This optional element is included within the body of a NOTIFY for the
"reg" event package when a GRUU is associated with the contact. The
contact URI and the GRUU are then both available to the watcher.
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Internet-Draft Reg Event GRUU Extension April 20064. Notifier Processing of SUBSCRIBE Requests
Unchanged from RFC 3680 [2].
5. Notifier Generation of NOTIFY Requests
A notifier for the "reg" event package [2] SHOULD include the <gruu>
element when a contact has an Instance ID and a GRUU is associated
with the combination of the AOR and the Instance ID. When present,
the <gruu> element MUST be be positioned as an instance of the <any>
element within the <contact> element.
6. Subscriber Processing of NOTIFY Requests
When a subscriber receives a "reg" event notification [2] with a
<contact> containing a <gruu>, it SHOULD use the GRUU in preference
to the corresponding <uri> when sending SIP requests to the contact.
Subscribers that are unaware of this extension will, as required by
[2], ignore the <gruu> element.
7. Sample reginfo Document
Note: This example and others in the following section are
indented for readability by the addition of a fixed amount of
whitespace to the beginning of each line. This whitespace is not
part of the example. The conventions of [8] are used to describe
representation of long message lines.
The following is an example registration information document
including the new element:
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Internet-Draft Reg Event GRUU Extension April 20068.2. Example: Implicit Registration
In an 3GPP IMS setting, a UA may send a single register message,
requesting assignment of a GRUU, as follows:
REGISTER sip:example.net SIP/2.0
From: <sip:user_aor_1@example.net>;tag=5ab4
To: <sip:user_aor_1@example.net>
Contact: <sip:ua.example.com>
;expires=3600
;+sip.instance="<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
Supported: path, gruu
Content-Length: 0
The response reports success of the registration and returns the GRUU
assigned for the combination of AOR, Instance ID, and Contact. It
also indicates (via the P-Associated-URI header [6]) that there are
two other associated AORs that may have been implicitly registered
using the same contact. But each of those implicitly registered AORs
will have had a unique GRUU assigned, and there is no way defined to
report that assignment in the response.
SIP/2.0 200 OK
From: <sip:user_aor_1@example.net>;tag=5ab4
To: <sip:user_aor_1@example.net>;tag=373392
Path: <sip:proxy.example.net;lr>
Service-Route: <sip:proxy.example.net;lr>
Contact: <sip:ua.example.com>
;expires=3600
;+sip.instance="<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>"
;gruu="sip:user_aor_1@example.net;opaque=hha9s8d-999a"
P-Associated-URI: <sip:user_aor_2@example.net>,
<sip:+358504821437@example.net;user=phone>
Content-Length: 0
The UA then subscribes to the 'reg' event package as follows:
SUBSCRIBE sip:user_aor_1@example.net SIP/2.0
From: <sip:user_aor_1@example.net>;tag=27182
To: <sip:user_aor_1@example.net>
Route: <sip:proxy.example.net;lr>
Event: reg
Expires: 3600
Accept: application/reginfo+xml
Contact: <sip:user_aor_1@example.net;opaque=hha9s8d-999a>
Content-Length: 0
(The successful response to the subscription is not shown.) Once the
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Internet-Draft Reg Event GRUU Extension April 2006
<allOneLine>
<gr:gruu>sip:user_aor_2@example.net
;opaque=hha9s8d-999b</gr:gruu>
</allOneLine>
</contact>
</registration>
<registration
aor="sip:+358504821437@example.net;user=phone"
id="a9"
state="active">
<contact id="94" state="active" event="created"
duration-registered="1" expires="3599">
<uri>
sip:ua.example.com
</uri>
<allOneLine>
<unknown-param name="+sip.instance">
"&lt;urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6&gt;"
</unknown-param>
</allOneLine>
<allOneLine>
<gr:gruu>sip:+358504821437@example.net;user=phone
;opaque=hha9s8d-999c</gr:gruu>
</allOneLine>
</contact>
</registration>
</reginfo>
The status indicates that the associated URIs all have the same
contact registered. It also includes the unique GRUU that has been
assigned to each. The UA may then retain those GRUUs for use when
establishing dialogs using the corresponding AORs.
9. XML Schema Definition
A GRUU document is an XML document that MUST be well-formed and
SHOULD be valid. GRUU documents MUST be based on XML 1.0 and MUST be
encoded using UTF-8. This specification makes use of XML namespaces
for identifying GRUU documents. The namespace URI for elements
defined for this purpose is a URN, using the namespace identifier
'ietf'. This URN is:
urn:ietf:params:xml:ns:gruuinfo
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Internet-Draft Reg Event GRUU Extension April 2006
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